Colloq Abstract - Andernach
Dec 15
11:00am Mountain
Heinz Andernach (Universidad de Guanajuato)
Giants all over: The Ubiquity of Mpc-scale Radio Galaxies
Abstract
Giant radio galaxies (GRGs) have projected linear sizes exceeding 1 Mpc. Only about 300 GRGs have been reported, in several dozens of papers. Since 2012 our search for new GRGs via visual inspection and automated algorithms of NVSS, WENSS, FIRST, SUMSS, TGSS-ADR1 and other survey images, as well as results from Radio Galaxy Zoo (RGZ),
have increased the number of GRGs to over 1200. We doubled the number of GRGs above 4 Mpc and have found some candidates over 5 Mpc size. Our follow-up with optical spectroscopy, plus JVLA imaging, has confirmed several dozen new giants, as well as the general reliability of photometric redshifts. While the median redshift of published GRGs is 0.25, our new GRGs and those of RGZ achieve a median z of 0.6, including about 15 QSOs at redshifts from 2 to 5.
I will show examples of the relative ease to find new GRGs, especially with simultaneous coverage of NVSS, FIRST, SDSS, and, since very recently, the ongoing 3-GHz VLA Sky Survey. GRGs show a large variety of radio morphologies, and I explore some statistical trends for lobe symmetry and compactness of their emission. Their host galaxies show all possible activity types, with LLAGNs dominating at low redshift and QSOs and Sy1's at high redshift. No significant trend of radio size with redshift is seen, posing a problem for standard cosmology.
